Instructions

1. Pick oranges that feel heavy and have thin, tight skin. A thick-skinned navel is mostly pith, and pith is the bitter part that does not improve with drying.
2. Scrub the skin well and leave it on. Most of the aroma in a dried orange slice is in the oil glands of the peel, and a peeled slice comes out tasting of very little.
3. Slice across the fruit at 5 mm on a mandolin if you have one. Cut too thin and the flesh vanishes and leaves you a ring of peel; too thick and the centre stays sticky for days.
4. Blot the cut slices on a towel before laying them out. Orange juice on the surface caramelises onto the tray and welds the slice to it.
5. Lay them flat with space around each and dehydrate at 57 °C for 17 hours. Turn them over once during the run, because the flesh releases juice that pools against the mesh.
6. They are done when the peel is hard and the flesh in the middle is no longer tacky to a fingertip. Let one cool and bend it: a finished slice is stiff and slightly leathery, and one that folds softly needs another couple of hours.
7. For slices you will hang up or float in a drink, push on until they are fully brittle. Those keep longer, but they are too hard to eat straight.
8. Store the cooled slices in an airtight jar out of the light for a year. If you grind them for powder, do it cold and use the powder within three months, because the peel oils that make it worth having are the first thing to go.